Wireless communication method and wireless communication terminal using multi-basic service identifier set

ABSTRACT

Provided is a wireless communication terminal that communicates wirelessly. The terminal includes: a transceiver; and a processor. The processor is configured to receive a frame through the transceiver, determine whether the frame is classified into an Intra-Basic Service Set (BSS) frame or an Inter-BSS frame according to a BSS from which the frame is transmitted, and access a channel according to whether the frame is an Intra-BSS frame or an Inter-BSS frame.

TECHNICAL FIELD

The present invention relates to a wireless communication method and awireless communication terminal using a multi-basic service identifierset.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelesscommunication technology that can provide a rapid wireless Internetservice to the mobile apparatuses has been significantly spotlighted.The wireless communication technology allows mobile apparatusesincluding a smart phone, a smart pad, a laptop computer, a portablemultimedia player, an embedded apparatus, and the like to wirelesslyaccess the Internet in home or a company or a specific service providingarea.

One of most famous wireless communication technology is wireless LANtechnology. Institute of Electrical and Electronics Engineers (IEEE)802.11 has commercialized or developed various technological standardssince an initial wireless LAN technology is supported using frequenciesof 2.4 GHz. First, the IEEE 802.11b supports a communication speed of amaximum of 11 Mbps while using frequencies of a 2.4 GHz band. IEEE802.11a which is commercialized after the IEEE 802.11b uses frequenciesof not the 2.4 GHz band but a 5 GHz band to reduce an influence byinterference as compared with the frequencies of the 2.4 GHz band whichare significantly congested and improves the communication speed up to amaximum of 54 Mbps by using an Orthogonal Frequency DivisionMultiplexing (OFDM) technology. However, the IEEE 802.11a has adisadvantage in that a communication distance is shorter than the IEEE802.11b. In addition, IEEE 802.11g uses the frequencies of the 2.4 GHzband similarly to the IEEE 802.11b to implement the communication speedof a maximum of 54 Mbps and satisfies backward compatibility tosignificantly come into the spotlight and further, is superior to theIEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n has been provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n has comeinto the spotlight. Among them, IEEE 802.11ac supports a wide bandwidth(80 to 160 MHz) in the 5 GHz frequencies. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11ac chipsets will supporteven operations in the 2.4 GHz band for the backward compatibility withthe existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of awireless interface accepted by 802.11n, such as a wider wirelessfrequency bandwidth (a maximum of 160 MHz), more MIMO spatial streams (amaximum of 8), multi-user MIMO, and high-density modulation (a maximumof 256 QAM). Further, as a scheme that transmits data by using a 60 GHzband instead of the existing 2.4 GHz/5 GHz, IEEE 802.11ad has beenprovided. The IEEE 802.11ad is a transmission standard that provides aspeed of a maximum of 7 Gbps by using a beamforming technology and issuitable for high bit rate moving picture streaming such as massive dataor non-compression HD video. However, since it is difficult for the 60GHz frequency band to pass through an obstacle, it is disadvantageous inthat the 60 GHz frequency band can be used only among devices in ashort-distance space.

Meanwhile, in recent years, as next-generation wireless communicationtechnology standards after the 802.11ac and 802.11ad, discussion forproviding a high-efficiency and high-performance wireless communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless communication technology environment,communication having high frequency efficiency needs to be providedindoors/outdoors under the presence of high-density terminals and baseterminals and various technologies for implementing the communicationare required.

Especially, as the number of devices using a wireless communicationtechnology increases, it is necessary to efficiently use a predeterminedchannel Therefore, required is a technology capable of efficiently usingbandwidths by simultaneously transmitting data between a plurality ofterminals and base terminals.

DISCLOSURE Technical Problem

An object of an embodiment of the present invention is to provide awireless communication method and a wireless communication terminalusing a multi-basic service identifier set.

Technical Solution

According to an embodiment of the present invention, a wirelesscommunication terminal that communicates wirelessly, the terminalcomprises a transceiver; and a processor, wherein the processor isconfigured to receive a frame through the transceiver, determine whetherthe frame is an Intra-Basic Service Set (BSS) frame or an Inter-BSSframe according to a BSS from which the frame is transmitted, and accessa channel according to whether the frame is an Intra-BSS frame or anInter-BSS frame.

A BSS of the wireless communication terminal may correspond to amultiple BSS identifier (BSSID) set. The multiple BSSID set may be a setof a BSSID of each of a plurality of BSSs classified into one group. Theprocessor may determine whether the frame is an Intra-BSS frame or anInter-BSS frame based on a Medium Access Control (MAC) address signaledin a MAC header of the frame and a plurality of BSSIDs included in themultiple BSSID set.

When the MAC address signaled in the MAC header of the frame matches anyone of the plurality of BSSIDs included in the multiple BSSID set, theprocessor may determine the frame as an Intra-BSS frame.

When a Transmitter Address or a Receiver Address signaled in the MACheader of the frame matches any one of the plurality of BSSIDs includedin the multiple BSSID set, the processor may determine that the frame isan Intra-BSS frame.

When the frame is an Intra-BSS frame and a receiver address (RA) of theframe does not indicate the wireless communication terminal, theprocessor may enter a power save state.

When the MAC address signaled in the MAC header of the frame matches anyone of a plurality of BSSIDs included in the multiple BSSID set and theRA of the frame does not indicate the wireless communication terminal,the processor may enter the power save state.

When a Receiver Address or a Transmitter Address of the frame is one ofthe plurality of BSSIDs included in the multiple BSSID set and theReceiver Address of the frame is not the MAC address of the wirelesscommunication terminal, the processor may the power save state.

The processor may maintain the power save state during a duration of aPLCP Protocol Data Unit (PPDU) including the frame.

The processor may separately set a Network Allocation Vector (NAV) foran Intra-BSS frame and a NAV for an Inter-BSS frame.

When the MAC address signaled in the MAC header of the frame matches anyone of the plurality of BSSIDs included in the multiple BSSID set, theprocessor may set the NAV for the Intra-BSS frame based on the frame.

A plurality of BSSs corresponding to the multiple BSSID set may have thesame BSS color value, and the BSS color may be information identifying aBSS signaled in a physical layer signaling field of a PLCP Protocol DataUnit (PPDU) including the frame.

The processor may apply a first Clear Channel Assessment (CCA) thresholdto accessing the channel when the frame is the Intra-BSS frame, andapply a second CCA threshold to accessing the channel when the frame isthe Inter-BSS frame. The second CCA threshold may be determined in aOverlapped BSS (OBSS) CCA level range. The OBSS CCA level range mayinclude values equal to or greater than the first CCA threshold.

According to an embodiment of the present invention, an operation methodof a wireless communication terminal that communicates wirelesslyincludes receiving a frame; determining whether the frame is anIntra-BSS frame or an Inter-BSS frame according to a BSS from which theframe is transmitted; and accessing a channel according to whether theframe is an Intra-Basic Service Set (BSS) frame or an Inter-BSS frame.

A BSS of the wireless communication terminal may correspond to amultiple BSS identifier (BSSID) set. The multiple BSSID set may be a setof a BSSID of each of a plurality of BSSs classified into one group. Thedetermining whether the frame is an Intra-BSS frame or an Inter-BSSframe may include determining whether the frame is an Intra-BSS frame oran Inter-BSS frame based on a medium access control (MAC) addresssignaled in a MAC header of the frame and a plurality of BSSIDs includedin the multiple BSSID set.

The determining whether the frame is the Intra-BSS frame or theInter-BSS frame may include, when the MAC address signaled in the MACheader of the frame matches one of the plurality of BSSIDs included inthe multiple BSSID set, determining the frame as an Intra-BSS frame.

The determining the frame as the Intra-BSS frame may include, when aTransmitter Address or a Receiver Address signaled in the MAC header ofthe frame matches any one of the plurality of BSSIDs included in themultiple BSSID set, determining that the frame is an Intra-BSS frame.

The method may further include, when the frame is an Intra-BSS frame anda receiver address (RA) of the frame does not indicate the wirelesscommunication terminal, entering a power save state.

The entering the power save state may include, when the MAC addresssignaled in the MAC header of the frame matches any one of a pluralityof BSSIDs included in the multiple BSSID set and the RA of the framedoes not indicate the wireless communication terminal, entering thepower save state.

The plurality of BSSs corresponding to the multiple BSSID set may havethe same BSS color value. The BSS color may be information identifying aBSS signaled in a physical layer signaling field of a PLCP Protocol DataUnit (PPDU) including the frame.

The accessing the channel may include applying a first Clear ChannelAssessment (CCA) threshold to accessing the channel when the frame isthe Intra-BSS frame, and applying a second CCA threshold to accessingthe channel when the frame is the Inter-BSS frame. The second CCAthreshold may be determined within a OBSS CCA level range. The OBSS CCAlevel range may be equal to or greater than the first CCA threshold.

Advantageous Effects

An embodiment of the present invention provides a wireless communicationmethod and a wireless communication terminal using a multi-basic serviceidentifier set.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a wireless LAN system according to an embodiment of thepresent invention.

FIG. 2 shows a wireless LAN system according to another embodiment ofthe present invention.

FIG. 3 shows a block diagram illustrating a configuration of a stationaccording to an embodiment of the inventive concept.

FIG. 4 shows a block diagram illustrating a configuration of an accesspoint according to an embodiment of the present invention.

FIG. 5 shows a process that a station sets an access point and a linkaccording to an embodiment of the present invention.

FIG. 6 shows a network for a virtual LAN according to an embodiment ofthe present invention.

FIG. 7 shows a signaling format of information on a multi-basic serviceidentifier set according to an embodiment of the present invention.

FIG. 8 shows a spatial reuse operation of a wireless communicationterminal when a wireless communication terminal according to anembodiment of the present invention uses a multiple BSSID set.

FIG. 9 shows a network for a virtual LAN according to an embodiment ofthe present invention.

FIG. 10 shows a power save operation of a wireless communicationterminal according to an embodiment of the present invention.

FIG. 11 shows the channel access operation of a wireless communicationterminal according to an embodiment of the present invention.

FIG. 12 shows the channel access operation of a wireless communicationterminal according to another embodiment of the present invention.

FIG. 13 shows a method of setting BSS color values of a plurality ofBSSs corresponding to a multiple BSSID set according to an embodiment ofthe present invention.

FIG. 14 shows a case where a wireless communication terminal accordingto an embodiment of the present invention enters a power save statebased on a MAC header of a frame received by the wireless communicationterminal.

FIG. 15 shows a case where, when a wireless communication terminalaccording to an embodiment of the present invention is included in a BSScorresponding to a multiple BSSID set, the wireless communicationterminal enters a power save state based on a MAC header of a framereceived by the wireless communication terminal.

FIG. 16 shows a method of displaying an identifier of a wirelesscommunication terminal included in a plurality of BSSs corresponding toa multiple BSSID set according to an embodiment of the presentinvention.

FIG. 17 shows a trigger frame format according to an embodiment of thepresent invention.

FIG. 18 shows a trigger frame format according to another embodiment ofthe present invention.

FIG. 19 shows a trigger frame format according to another embodiment ofthe present invention.

FIG. 20 shows an OFDMA backoff operation of a wireless communicationterminal according to an embodiment of the present invention.

FIG. 21 shows the operation of a wireless communication terminalaccording to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstructed as limited to the embodiments set forth herein. Parts notrelating to description are omitted in the drawings in order to clearlydescribe the present invention and like reference numerals refer to likeelements throughout.

Furthermore, when it is described that one comprises (or includes orhas) some elements, it should be understood that it may comprise (orinclude or has) only those elements, or it may comprise (or include orhave) other elements as well as those elements if there is no specificlimitation.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2015-0175411 (2015 Dec. 9), Nos. 10-2015-0186868(2015 Dec. 24), Nos. 10-2016-0004464 (2016 Jan. 13), and Nos.10-2016-0114821 (2016 Sep. 7) filed in the Korean Intellectual PropertyOffice and the embodiments and mentioned items described in therespective applications are included in the Detailed Description of thepresent application.

FIG. 1 is a diagram illustrating a wireless communication systemaccording to an embodiment of the present invention. For convenience ofdescription, an embodiment of the present invention is described throughthe wireless LAN system. The wireless LAN system includes one or morebasic service sets (BSS) and the BSS represents a set of apparatuseswhich are successfully synchronized with each other to communicate witheach other. In general, the BSS may be classified into an infrastructureBSS and an independent BSS (IBSS) and FIG. 1 illustrates theinfrastructure BSS between them.

As illustrated in FIG. 1, the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA1, STA2, STA3, STA4, and STA5, accesspoints PCP/AP-1 and PCP/AP-2 which are stations providing a distributionservice, and a distribution system (DS) connecting the multiple accesspoints PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a wireless medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, a term ‘terminal’ may beused to refer to a concept including a wireless LAN communication devicesuch as non-AP STA, or an AP, or both terms. A station for wirelesscommunication includes a processor and a transceiver and according tothe embodiment, may further include a user interface unit and a displayunit. The processor may generate a frame to be transmitted through awireless network or process a frame received through the wirelessnetwork and besides, perform various processing for controlling thestation. In addition, the transceiver is functionally connected with theprocessor and transmits and receives frames through the wireless networkfor the station.

The access point (AP) is an entity that provides access to thedistribution system (DS) via wireless medium for the station associatedtherewith. In the infrastructure BSS, communication among non-APstations is, in principle, performed via the AP, but when a direct linkis configured, direct communication is enabled even among the non-APstations. Meanwhile, in the present invention, the AP is used as aconcept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense.

A plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, a plurality of BSSsconnected through the distribution system is referred to as an extendedservice set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless communicationsystem according to another embodiment of the present invention. Forconvenience of description, another embodiment of the present inventionis described through the wireless LAN system. In the embodiment of FIG.2, duplicative description of parts, which are the same as or correspondto the embodiment of FIG. 1, will be omitted.

Since a BSS3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA6 and STA7 are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA6 and STA7 may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention.

As illustrated in FIG. 3, the station 100 according to the embodiment ofthe present invention may include a processor 110, a transceiver 120, auser interface unit 140, a display unit 150, and a memory 160.

First, the transceiver 120 transmits and receives a wireless signal suchas a wireless LAN physical layer frame, or the like and may be embeddedin the station 100 or provided as an exterior. According to theembodiment, the transceiver 120 may include at least one transmit andreceive module using different frequency bands. For example, thetransceiver 120 may include transmit and receive modules havingdifferent frequency bands such as 2.4 GHz, 5 GHz, and 60 GHz. Accordingto an embodiment, the station 100 may include a transmit and receivemodule using a frequency band of 6 GHz or more and a transmit andreceive module using a frequency band of 6 GHz or less. The respectivetransmit and receive modules may perform wireless communication with theAP or an external station according to a wireless LAN standard of afrequency band supported by the corresponding transmit and receivemodule. The transceiver 120 may operate only one transmit and receivemodule at a time or simultaneously operate multiple transmit and receivemodules together according to the performance and requirements of thestation 100. When the station 100 includes a plurality of transmit andreceive modules, each transmit and receive module may be implemented byindependent elements or a plurality of modules may be integrated intoone chip.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, for example, the transceiver 120, andthe like. The processor 110 may be a modulator and/or demodulator whichmodulates wireless signal transmitted to the transceiver 120 anddemodulates wireless signal received from the transceiver 120. Theprocessor 110 controls various operations of wireless signaltransmission/reception of the station 100 according to the embodiment ofthe present invention. A detailed embodiment thereof will be describedbelow.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. For example, theprocessor 110 and the transceiver 120 may be implemented while beingintegrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, for example, the user interface unit 140 and thedisplay unit 150 may be optionally provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention.

As illustrated in FIG. 4, the AP 200 according to the embodiment of thepresent invention may include a processor 210, a transceiver 220, and amemory 260. In FIG. 4, among the components of the AP 200, duplicativedescription of parts which are the same as or correspond to thecomponents of the station 100 of FIG. 2 will be omitted.

Referring to FIG. 4, the AP 200 according to the present inventionincludes the transceiver 220 for operating the BSS in at least onefrequency band. As described in the embodiment of FIG. 3, thetransceiver 220 of the AP 200 may also include a plurality of transmitand receive modules using different frequency bands. That is, the AP 200according to the embodiment of the present invention may include two ormore transmit and receive modules among different frequency bands, forexample, 2.4 GHz, 5 GHz, and 60 GHz together. Preferably, the AP 200 mayinclude a transmit and receive module using a frequency band of 6 GHz ormore and a transmit and receive module using a frequency band of 6 GHzor less. The respective transmit and receive modules may performwireless communication with the station according to a wireless LANstandard of a frequency band supported by the corresponding transmit andreceive module. The transceiver 220 may operate only one transmit andreceive module at a time or simultaneously operate multiple transmit andreceive modules together according to the performance and requirementsof the AP 200.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. The processor 210 may be a modulatorand/or demodulator which modulates wireless signal transmitted to thetransceiver 220 and demodulates wireless signal received from thetransceiver 220. The processor 210 controls various operations such asradio signal transmission/reception of the AP 200 according to theembodiment of the present invention. A detailed embodiment thereof willbe described below.

FIG. 5 is a diagram schematically illustrating a process in which a STAsets a link with an AP.

Referring to FIG. 5, the link between the STA 100 and the AP 200 is setthrough three steps of scanning, authentication, and association in abroad way. First, the scanning step is a step in which the STA 100obtains access information of BSS operated by the AP 200. A method forperforming the scanning includes a passive scanning method in which theAP 200 obtains information by using a beacon message (S101) which isperiodically transmitted and an active scanning method in which the STA100 transmits a probe request to the AP (S103) and obtains accessinformation by receiving a probe response from the AP (S105).

The STA 100 that successfully receives wireless access information inthe scanning step performs the authentication step by transmitting anauthentication request (S107 a) and receiving an authentication responsefrom the AP 200 (S107 b). After the authentication step is performed,the STA 100 performs the association step by transmitting an associationrequest (S109 a) and receiving an association response from the AP 200(S109 b).

Meanwhile, an 802.1X based authentication step (S111) and an IP addressobtaining step (S113) through DHCP may be additionally performed. InFIG. 5, the authentication server 300 is a server that processes 802.1Xbased authentication with the STA 100 and may be present in physicalassociation with the AP 200 or present as a separate server.

In a specific embodiment, the AP 200 may be a wireless communicationterminal that allocates a communication medium resource and performsscheduling in an independent network, such as an ad-hoc network, whichis not connected to an external distribution service. In addition, theAP 200 may be at least one of a base station, an eNB, and a transmissionpoint TP.

FIG. 6 shows a network for a virtual LAN according to an embodiment ofthe present invention.

A plurality of virtual LANs (VLANs) may constitute one network. In theembodiment of FIG. 6, one Ethernet switch (802.3 bridge) connects anAirport VLAN, a Lounge VLAN, and a Management VLAN. In a networkcomposed of a plurality of VLANs, the Ethernet switch (802.3 bridge) maycontrol QoS by virtual LAN. Specifically, the Ethernet switch (802.3bridge) may control the traffic speed according to the virtual LAN.Specifically, the Ethernet switch (802.3 bridge) may control the trafficspeed according to the virtual LAN. Specifically, the Ethernet switch(802.3 bridge) may assign different access rights to each virtual LAN.

At this time, the network may include a plurality of physical accesspoints. However, when there are a plurality of physical access points inone network, Due to the management frames transmitted by the pluralityof access points, the time for the frame for data transmission to occupythe channel may be very short. Therefore, in a network, as shown in FIG.6, one wireless communication terminal may operate a plurality of BSSs.A method in which one wireless communication terminal operates aplurality of BSSs will be described in detail with reference to FIG. 7.Also, a frame in this specification refers to a MAC frame unlessotherwise specified.

FIG. 7 shows a signaling format of information on a multi-basic serviceidentifier set according to an embodiment of the present invention.

A wireless communication terminal may signal information on a pluralityof BSSs through one management frame. Specifically, the wirelesscommunication terminal may signal information on a multiple BSSID setincluding a plurality of BSS identifiers (BSSIDs) through a managementframe. A multiple BSSID set is a BSSID set of a plurality of BSSsclassified into one group. When the wireless communication terminal usesa multiple BSSID set, since the wireless communication terminal signalsa plurality of BSSs through one management frame, it may increase theamount of time that a data frame may occupy a channel. In a specificembodiment, the wireless communication terminal may set the referenceBSSID representing the multiple BSSID set to the BSS informationindicated by the management frame, and insert information on a multipleBSSID set into the management frame. The information on the multipleBSSID set may include information related to the maximum number of theplurality of BSSIDs included in the multiple BSSID set. Specifically,the information on the multiple BSSID set may be the multiple BSSIDelements in FIG. 7(a). At this time, the information on the multipleBSSID set may include sub-elements. Further, the ID value foridentifying the sub-element may be the same as that of the embodiment ofFIG. 7(b).

Multiple BSSID element may include a Element ID field. The Element IDfield is an identifier indicating a multiple BSSID element. In addition,the multiple BSSID element may include a Length field. The Length fieldis a field indicating the length of multiple BSSID elements. Inaddition, the multiple BSSID element may indicate a MaxBSSID indicatorfield. At this time, the MaxBSSID indicator field indicates informationrelated to the maximum number of BSSIDs that a multiple BSSID set mayinclude. Specifically, when the value indicated by the MaxBSSIDindicator field is n, the maximum number of BSSIDs that a multiple BSSIDset may include is 2^(n). The maximum number of BSSIDs is the numberincluding the reference BSSID. In addition, the multiple BSSID elementmay include an Optional Subelements field. Optional Subelements mayinclude information on the BSS indicated by the Nontransmitted BSSID.The Nontransmitted BSSID indicates the BSSID included in the multipleBSSID set in addition to the reference BSSID. Specifically, the OptionalSubelements field may include a Nontransmitted BSSID profile, which isinformation on the BSS indicated by the Nontransmitted BSSID. TheOptional Subelements field may include only information on the BSSindicated by a part of Nontransmitted BSSIDs. At this time, the wirelesscommunication terminal receiving the management frame may obtaininformation on the BSS indicated by the remaining Nontransmitted BSSIDbased on the beacon frame or the probe response frame. In addition, thewireless communication terminal receiving the management frame mayobtain information on the BSS indicated by the remaining NontransmittedBSSID by transmitting a probe request frame.

The information on the BSS indicated by the Nontransmitted BSSID may bean element included in the Nontransmitted BSSID Capability element andthe beacon frame body. Specifically, the element that may be included inthe beacon frame body may be at least one of an SSID, a multipleBSSID-index sub-element, and an FMD Descriptor element. In addition, thesame information as the BSS information indicated by the reference BSSIDamong the information on the BSS indicating the Nontransmitted BSSID maybe omitted. Specifically, at least one of a Timestamp and BeaconInterval field indicated by a Nontransmitted BSSID, a DSSS ParameterSet, an IBSS Parameter Set, Country, Channel Switch Announcement,Extended Channel Switch Announcement, Wide Bandwidth Channel Switch,Transmit Power Envelope, Supported Operating Classes, IBSS DFS, ERPInformation, HT Capabilities, HT Operation, VHT Capabilities, and a VHTOperation element may be the same as the BSS indicated by the referenceBSSID.

In addition, the Optional Sub-element field may include a vendorspecific element. A wireless communication terminal receiving amanagement frame including information on a multiple BSSID set mayobtain information on a multiple BSSID set from a management frame. Atthis time, the wireless communication terminal may obtain the BSSIDincluded in the multiple BSSID set based on the information on themultiple BSSID set and the reference BSSID. Specifically, the wirelesscommunication terminal may obtain the BSSID included in the multipleBSSID set through the following equation.

BSSID(i)=BSSID_A|BSSID_B

At this time, BSSID_A is a BSSID in which (48-n) Most Significant Bit(MSB) values are equal to (48-n) MSB values of the reference BSSID and nLeast Significant Bit (LSB) values are 0. Also, BSSID_B is a BSSID inwhich (48-n) MSB values are 0, and the n LSB values are the remainingvalue (mod) when dividing the sum of n LSBs and i of the reference BSSIDby 2^(n).

Due to the spread of mobile devices and the supply of wirelesscommunication, wireless communication terminals are increasinglycommunicating in a dense environment. Particularly, the number of caseswhere a wireless communication terminal communicates in an environmentin which a plurality of BSSs are overlapped is increasing. When multipleBSSs are overlapped, the communication efficiency of the wirelesscommunication terminal may be degraded due to interference with otherwireless communication terminals. In particular, when a frequency bandis used through a contention procedure, a wireless communicationterminal may not secure even a transmission opportunity due tointerference with other wireless communication terminals. To solve thisproblem, a wireless communication terminal may perform a spatial reuse(SR) operation. Specifically, the SR operation may include an operationof accessing the channel depending on whether the received frame is aframe transmitted from a BSS including a wireless communication terminalor a frame transmitted from another BSS. In a specific embodiment, theoperation of accessing the channel may include at least one of a CCAoperation, a deferral operation, and a Network Allocation Vector (NAV)setting operation. At this time, the NAV represents the time when theradio resource is occupied by the transmission of another wirelesscommunication terminal. The NAV may be maintained regardless of theClear Channel Assessment (CCA) results. Specifically, the wirelesscommunication terminal may adjust a Clear Channel Assessment (CCA)threshold value according to whether a frame received by the wirelesscommunication terminal is a frame transmitted from a BSS including awireless communication terminal or a frame transmitted from an OBSS. Atthis time, in the case of the frame transmitted from the OBSS, thewireless communication terminal may apply a CCA threshold value that islarger than a CCA threshold value applied when the frame is transmittedfrom the BSS including the wireless communication terminal. At thistime, the CCA threshold value indicates a reference value fordetermining that the channel is busy or idle. In addition, the wirelesscommunication terminal may adjust the transmission power of the PLCProtocol Data Unit (PPPU) transmitted during the SR operation. Whenmultiple BSSID sets are used, the SR operation of the wirelesscommunication terminal is a problem. When multiple BSSID sets are used,the SR operation of the wireless communication terminal will bedescribed with reference to FIG. 8 to FIG. 16.

FIG. 8 shows a spatial reuse operation of a wireless communicationterminal when a wireless communication terminal according to anembodiment of the present invention uses a multiple BSSID set.

For convenience of explanation, a BSS including a wireless communicationterminal is referred to as Intra-BSS, and a basic service set overlappedwith Intra-BSS is referred to as an Overlapped Basic Service Set (OBSS).In addition, the PPDU transmitted from the Intra-BSS is referred to asan Intra-BSS PPDU, and the frame transmitted from the OBSS is referredto as an OBSS PPDU or an Inter-BSS PPDU. In addition, a frametransmitted in the Intra-BSS is referred to as an Intra-BSS frame, and aframe transmitted in the OBSS is referred to as an OBSS frame or anInter-BSS frame. In addition, when the Intra-BSS frame is transmitted,the magnitude of the CCA threshold value applied by the wirelesscommunication terminal is referred to as a general CCA level. When theInter-BSS frame is transmitted, the magnitude of the CCA threshold valueapplied by the wireless communication terminal is referred to as theOBSS CCA level. In particular, when an Inter-BSS frame is transmitted,the magnitude of the CCA threshold value used for preamble detection(PD) by a wireless communication terminal is referred to as an OBSS PDlevel. At this time, the OBSS CCA level may be a value which is equal toor greater than the general CCA level value.

As described above, the wireless communication terminal may access thechannel based on whether the received PPDU is Intra-BSS PPDU orInter-BSS PPDU. Specifically, the wireless communication terminal mayaccess the channel based on whether the received frame is an Intra-BSSframe or an Inter-BSS frame. When a multiple BSSID set is used, thewireless communication terminal may regard a plurality of BSSsidentified by each of the plurality of BSSIDs included in the samemultiple BSSID set as the same BSS. When a multiple BSSID set is used,the wireless communication terminal may regard a plurality of BSSsidentified by each of the plurality of BSSIDs included in the samemultiple BSSID set as the same BSS. For convenience of explanation, theBSSID of the BSS including the wireless communication terminal isreferred to as a first BSSID, and a BSSID other than the first BSSID isreferred to as a second BSSID. When the first BSSID is included in themultiple BSSID set including the second BSSID, the wirelesscommunication terminal may determine the frame transmitted from the BSSidentified by the second BSSID as an Intra-BSS frame. In addition, whenthe first BSSID is not included in any multiple BSSID set or the secondBSSID is not included in the multiple BSSID set including the firstBSSID, the wireless communication terminal may determine the frametransmitted from the BSS identified by the second BSSID as an inter-BSSframe. Specifically, when the first BSSID is included in the multipleBSSID set including the second BSSID, and the wireless communicationterminal detects a frame transmitted from the BSS identified by thesecond BSSID, the wireless communication terminal may apply the CCAthreshold value as a general CCA level instead of the OBSS CCA level.When the first BSSID is not included in any multiple BSSID set or thesecond BSSID is not included in the multiple BSSID set including thefirst BSSID and the wireless communication terminal detects a frametransmitted from the BSS identified by the second BSSID, the wirelesscommunication terminal may apply the OBSS CCA level as the CCA thresholdvalue.

In the embodiment of FIG. 8(a), the tenth station STA10 is associatedwith the first virtual access point VAP1, and the twentieth stationSTA20 is associated with the second virtual access point VAP2. Inaddition, the BSSs operated by each of the first virtual access pointVAP1 to the third virtual access point VAP3 all have a BSSID included inthe same multiple BSSID set. At this time, the twentieth station STA20determines the PPDU transmitted from the first virtual access point VAP1as the intra-BSS PPDU. The network relationship of the embodiment ofFIG. 8(a) is applied as it is to FIGS. 8(b), 8(c) and 8(d).

In addition, the wireless communication terminal may change the NAVsetting depending on whether the received frame is an Intra-BSS frame oran Inter-BSS frame. Specifically, the wireless communication terminalmay separately maintain the NAV for the intra-BSS frame and the NAV forthe inter-BSS frame. At this time, when the wireless communicationterminal receives the Intra-BSS frame, the wireless communicationterminal may set or update the NAV for the intra-BSS frame based on thereceived Intra-BSS frame. In addition, when the frame received by thewireless communication terminal may not be determined as an Intra-BSSframe or an Inter-BSS frame, the wireless communication terminal mayupdate the NAV for the inter-BSS frame based on the received frame. Inaddition, when the wireless communication terminal receives theInter-BSS frame, the wireless communication terminal may set or updatethe NAV for the inter-BSS frame based on the received Inter-BSS frame.Accordingly, when the first BSSID is included in the multiple BSSID setincluding the second BSSID and the wireless communication terminalreceives the frame transmitted from the BSS identified by the secondBSSID, the wireless communication terminal may set or update the NAV forthe Intra-BSS frame based on the frame transmitted in the BSS identifiedby the second BSSID. When the first BSSID is not included in anymultiple BSSID set or the second BSSID is not included in the multipleBSSID set including the first BSSID and the wireless communicationterminal receives the frame transmitted from the BSS identified by thesecond BSSID, the wireless communication terminal may set or update theNAV for the Inter-BSS frame based on the frame transmitted in the BSSidentified by the second BSSID. In a specific embodiment, when thewireless communication terminal receives the CF-END frame from the OBSS,the wireless communication terminal may not reset the NAV set by theIntra-BSS frame. Therefore, when the first BSSID is included in themultiple BSSID set including the second BSSID, and the wirelesscommunication terminal receives the CF-END frame transmitted from theBSS identified by the second BSSID, the wireless communication terminalmay reset the NAV set by the Intra-BSS frame and maintain the NAV set bythe Inter-BSS frame as before. When the first BSSID is not included inany of the multiple BSSID set or the second BSSID is not included in themultiple BSSID set including the first BSSID and the wirelesscommunication terminal receives the CF-END frame transmitted from theBSS identified by the second BSSID, the wireless communication terminalmay reset the NAV set by the inter-BSS frame and maintain the NAV set bythe Intra-BSS frame as before. Specifically, the wireless communicationterminal may operate as in the embodiment of FIGS. 8(b) and 8(c).

In the embodiment of FIG. 8(b), the twentieth station STA20 receives thePPDU transmitted from the first virtual access point VAP1. The BSSIDidentifying the BSS of the first virtual access point VAP1 is includedin the multiple BSSID set including the BSSID identifying the BSS of thetwentieth station STA20. Therefore, the twentieth station STA 20 setsthe NAV for the Intra-BSS frame. At this time, the twentieth stationSTA20 receives the CF-END frame transmitted from the BSS (OBSS) otherthan the BSS operated by the first virtual access point VAP1 to thethird virtual access point VAP3. The twentieth station STA20 does notreset the NAV for the Intra-BSS frame.

In the embodiment of FIG. 8(c), the twentieth station STA20 receives thePPDUs transmitted from the BSS (OBSS) other than the BSS operated by thefirst virtual access point VAP1 to the third virtual access point VAP3.At this time, the twentieth station STA20 sets the NAV based on thereceived PPDU. The twentieth station STA20 receives the CF-END framefrom the first virtual access point VAP1. The BSSID identifying the BSSof the first virtual access point VAP1 is included in the multiple BSSIDset including the BSSID identifying the BSS of the twentieth stationSTA20. Therefore, the twentieth station STA20 resets the NAV for theintra-BSS frame and does not reset the NAV for the inter-BSS frame.

When the wireless communication terminal receives the trigger frame fortriggering the transmission of the wireless communication terminal, thewireless communication terminal may transmit a trigger-based PPDU basedon the trigger frame regardless of the set NAV. Specifically, when theNAV of the wireless communication terminal is set by the access pointthat transmits the trigger frame, the wireless communication terminalmay transmit trigger-based the PPDU regardless of the set NAV. Inanother specific embodiment, when the response to the trigger frameincludes an ACK frame and the length of the response is limited to lessthan the reference value, the wireless communication terminal maytransmit the trigger-based PPDU regardless of the set NAV. In anotherspecific embodiment, when the NAV of the wireless communication terminalis set by the Intra-BSS frame, the wireless communication terminal maytransmit the trigger-based PPDU regardless of the set NAV. In anotherspecific embodiment, when the BSSID of the BSS in which the frame forsetting the NAV of the wireless communication terminal is transmittedand the BSSID of the BSS including the wireless communication terminalare included in the same multiple BSSID set, the wireless communicationterminal may transmit the trigger-based PPDU regardless of the set NAV.Specifically, the wireless communication terminal may operate as in theembodiment of FIG. 8(d).

In the embodiment of FIG. 8(d), the twentieth station STA20 receives thePPDU transmitted by the first virtual access point VAP1. The BSSIDidentifying the BSS of the first virtual access point VAP1 is includedin the multiple BSSID set including the BSSID identifying the BSS of thetwentieth station STA20. Therefore, the twentieth station STA20 sets theNAV for the intra-BSS frame based on the received PPDU. The twentiethstation STA20 receives the CF-END frame from the first virtual accesspoint VAP1 but fails to decode the CF-END. The twentieth station STA20receives the trigger frame from the second virtual access point VAP2.The NAV set in the twentieth station STA20 is set based on the PPDUtransmitted by the first virtual access point AP and the BSSIDidentifying the BSS of the first virtual access point VAP1 is includedin the multiple BSSID set including the BSSID identifying the BSS of thetwentieth station STA20. Therefore, the twentieth station STA 20 maytransmit the trigger-based PPDU regardless of the set NAV.

The wireless communication terminal may determine, based on the BSScolor signaled in the physical layer of the received frame, whether thereceived frame is an Inter-BSS frame or an Intra-BSS frame. At thistime, the BSS color is information for identifying the BSS.Specifically, when the BSS color identifying the BSS including thewireless communication terminal is the same as the BSS color signaled inthe physical layer of the received frame, the wireless communicationterminal may determine the received frame as an Intra-BSS frame. Inaddition, when the BSS color identifying the BSS including the wirelesscommunication terminal and the BSS color signaled in the physical layerof the received frame are different, the wireless communication terminalmay determine the received frame as an Inter-BSS frame. In addition, thewireless communication terminal may determine, based on the MAC addresssignaled in the MAC layer of the received frame, whether the receivedframe is an Inter-BSS frame or an Intra-BSS frame. Specifically, thewireless communication terminal may determine, based on the addressfield of the received frame, whether the received frame is an Inter-BSSframe or an Intra-BSS frame. When the MAC address signaled in the MAClayer matches the MAC address or the BSSID of the access point operatingthe BSS including the wireless communication terminal in the specificembodiment, the wireless communication terminal may determine thereceived frame as an Intra-BSS frame. At this time, the MAC addresssignaled in the MAC layer may include Individual/Group bit signalingindicating whether the MAC address is a group MAC address. In this case,the wireless communication terminal may determine that value excludingthe Individual/Group bit from the MAC address signaled in the MAC layermatches the MAC address of the access point operating the BSS includingthe wireless communication terminal or the BSSID of the BSS includingthe wireless communication terminal.

Therefore, in order to consider a plurality of BSSs identified by eachof the plurality of BSSIDs included in the same multiple BSSID set asthe same BSS during the SR operation of the wireless communicationterminal, it is necessary to determine the information related to theBSS color and the MAC address. Specifically, the wireless communicationterminal compares the MAC address signaled in the MAC layer of thereceived frame with the multiple BSSID set including the BSSID of theBSS including the wireless communication terminal and determines whetherthe received frame is an Intra-BSS frame or an Inter-BSS frame. When theMAC address signaled in the MAC layer of the received frame is matchedwith any one of the plurality of BSSIDs included in the multiple BSSIDset including the BSSID of the BSS including the wireless communicationterminal in a specific embodiment, the wireless communication terminalmay determine the received frame as an Intra-BSS frame. In anotherspecific embodiment, when the MAC address signaled in the MAC layer ofthe received frame is not matched with any one of the plurality ofBSSIDs included in the multiple BSSID set including the BSSID of the BSSincluding the wireless communication terminal, the wirelesscommunication terminal may determine the received frame as an Inter-BSSframe. At this time, the wireless communication terminal may obtaininformation on the multiple BSSID set from the management frame asdescribed above. Specifically, the information on the multiple BSSID setmay be the multiple BSSID set elements described above.

In addition, a BSS corresponding to each of a plurality of BSSIDsincluded in the same multiple BSSID set may be set to the same BSScolor. Specifically, each of the plurality of access points operatingthe BSS corresponding to each of the plurality of BSSIDs included in thesame multiple BSSID set may set the BSS color values of the BSSscorresponding to the plurality of BSSIDs to be the same. At this time, aplurality of BSSs corresponding to the multiple BSSID set may beoperated by one wireless communication terminal. In another specificembodiment, a BSS color corresponding to a plurality of BSSIDs includedin a multiple BSSID set may be signaled. Specifically, the access pointmay signal a BSS color corresponding to a plurality of BSSIDs includedin a multiple BSSID set. The BSS color setting method and the BSS colorsignaling method for multiple BSSID sets will be described withreference to FIGS. 9 to 12.

FIG. 9 shows a network for a virtual LAN according to an embodiment ofthe present invention.

As described above, the BSS color values of a plurality of BSSscorresponding to the multiple BSSID set may all be set to be the same.At this time, the plurality of BSSs corresponding to the multiple BSSIDset indicate a plurality of BSSs identified by the plurality of BSSIDsincluded in the multiple BSSID set. Specifically, a plurality of accesspoints operating each of a plurality of BSSs corresponding to aplurality of BSSIDs may all set the same BSS color. The BSS color may besignaled through the signaling field of the physical layer.Specifically, the BSS color may be signaled through the HE-SIG-A field.As described above, the wireless communication terminal may perform theSR operation based on the BSS color. Specifically, the wirelesscommunication terminal may access the channel based on the BSS color. Inaddition, the wireless communication terminal may perform a power saveoperation based on the BSS color.

In the embodiment of FIG. 9, the BSSs operated by the first virtualaccess point VAP1 to the third virtual access point VAP3 all have thesame BSS color value X. All other settings of the network are the sameas in FIG. 6. A specific power save operation will be described withreference to FIG. 10, and a specific CCA operation will be describedwith reference to FIG. 11 and FIG. 12.

FIG. 10 shows a power save operation of a wireless communicationterminal according to an embodiment of the present invention.

The wireless communication terminal may enter a power save state forpower saving when the recipient of the Intra-BSS frame is not a wirelesscommunication terminal. At this time, the power save state may bereferred to as a doze state. Specifically, the power save state mayindicate that some function is inactive for power saving. In a specificembodiment, when the frame received by the wireless communicationterminal is an Intra-BSS frame and the recipient of the frame receivedby the wireless communication terminal is not a wireless communicationterminal, the wireless communication terminal may enter the power savestate. For example, when the BSS color signaled through the PPDUreceived by the wireless communication terminal is the same as the BSScolor of the wireless communication terminal and the recipient of theframe included in the received PPDU is not the wireless communicationterminal, the wireless communication terminal may enter the power savestate.

In a case where the BSS color values of a plurality of BSSscorresponding to the multiple BSSID set are all set to be the same, evenwhen the wireless communication terminal receives the PPDU transmittedfrom the BSS identified by the BSSID included in the multiple BSSID setthat includes the BSSID of the BSS including the wireless communicationterminal other than the BSS including the wireless communicationterminal, the wireless communication terminal may enter the power savestate.

In the embodiment of FIG. 10, the first case case 1 is the case wherethe BSS color values of a plurality of BSSs corresponding to themultiple BSSID set are not all set to be the same, and the second casecase 2 is the case where the BSS color values of a plurality of BSSscorresponding to the multiple BSSID set are all set to be the same. Atthis time, the access point AP operating the BSS identified by thesecond BSSID BSSID(2) and the station STA of BSSID(2) included in theBSS identified by the second BSSID BSSID(2) transmit/receive PPDUs. Atthis time, the station STA of BSSID(1) included in the BSS identified bythe first BSSID BSSID(1) other than the second BSSID BSSID(2) may notenter a power save state in the first case Case 1. However, the stationSTA of BSSID(1) included in the BSS identified by the first BSSIDBSSID(1) that is not the second BSSID BSSID(2) may check the BSS colorsignaled by the PPDU and enter the power save state in the second caseCase 2. The wireless communication terminal may increase the powerefficiency when a multiple BSSID set is used through this operation.

FIG. 11 shows the channel access operation of a wireless communicationterminal according to an embodiment of the present invention.

As described above, the wireless communication terminal may adjust theCCA threshold value according to whether the received frame is anInter-BSS frame or an Intra-BSS frame. Specifically, when the receivedframe is an Inter-BSS frame, the wireless communication terminal mayapply the OBSS CCA level not the general CCA level as the CCA thresholdvalue. At this time, the OBSS CCA level may be a value which is equal toor greater than the general CCA level. For convenience of explanation,the BSSID of the BSS including the wireless communication terminal isreferred to as a first BSSID, and a BSSID other than the first BSSID isreferred to as a second BSSID. When the BSS color values of theplurality of BSSs corresponding to the multiple BSSID set are all set tobe the same and the first BSSID is included in the multiple BSSID setincluding the second BSSID, even when the wireless communicationterminal receives the PPDU transmitted from the BSS identified by thesecond BSSID, the general CCA level, not the OBSS CCA level, may beapplied as the CCA threshold value. A specific operation of a wirelesscommunication terminal will be described with reference to FIG. 11.

In the embodiment of FIG. 11, the first case case 1 is the case wherethe BSS color values of a plurality of BSSs corresponding to themultiple BSSID set are not all set to be the same, and the second casecase 2 is the case where the BSS color values of a plurality of BSSscorresponding to the multiple BSSID set are all set to be the same. Atthis time, the PPDU is transmitted from the BSS identified by the secondBSSID BSSID(2). At this time, the station STA of BSSID(1) included inthe BSS identified by the first BSSID BSSID(1) that is not the secondBSSID BSSID(2) determines the BSS color signaled by the PPDU.Specifically, the station STA of BSSID(1) included in the BSS identifiedby the first BSSID BSSID(1) may obtain the BSS color from the signalingfield of the PPDU. At this time, the signaling field may be the HE-SIG-Afield. In the first case Case 1, since the BSS color obtained from thesignaling field of the PPDU differs from the BSS color of the BSSidentified by the first BSSID BSSID(1) in the station STA of BSSID(1)included in the BSS identified by the first BSSID BSSID(1), the stationSTA of BSSID(1) included in the BSS identified by the first BSSIDBSSID(1) applies the OBSS PD CCA level to the CCA threshold value. Sincethe received signal strength (RSSI) value is less than the OBSS PD CCAlevel, the station STA of BSSID(1) included in the BSS identified by thefirst BSSID BSSID(1) accesses the channel. Specifically, the station STAof BSSID(1) included in the BSS identified by the first BSSID BSSID(1)determines that the channel is idle. In the first case Case 2, since theBSS color obtained from the signaling field of the PPDU is the same asthe BSS color of the BSS identified by the first BSSID BSSID(1) in thestation STA of BSSID(1) included in the BSS identified by the firstBSSID BSSID(1), the station STA of BSSID(1) included in the BSSidentified by the first BSSID BSSID(1) applies the general PD CCA levelto the CCA threshold value. Since the received signal strength (RSSI)value is greater than general CCA level, the station STA of BSSID(1)included in the BSS identified by the first BSSID BSSID(1) does notaccess the channel. Specifically, the station STA of BSSID(1) includedin the BSS identified by the first BSSID BSSID(1) determines that thecorresponding channel is busy. Through this operation, the wirelesscommunication terminal may prevent a transmission collision between BSSscorresponding to the same multiple BSSID set.

In addition, as described above, the wireless communication terminal maydetermine, based on the MAC address signaled in the MAC layer of thereceived frame, whether the received frame is an Inter-BSS frame or anIntra-BSS frame. Particularly, when a legacy PPDU in which the BSS coloris not signaled in the physical layer is transmitted, the wirelesscommunication terminal may determine, based on the MAC address signaledin the MAC layer of the received frame, whether the received frame is anInter-BSS frame or an Intra-BSS frame. At this time, the wirelesscommunication terminal may regard a plurality of BSSs corresponding tothe same multiple BSSID as the same BSS as described above.

When the BSS color values of a plurality of BSSs corresponding to themultiple BSSID set are all set to be the same, the system complexity maybe reduced as compared with the case of signaling a BSS colorcorresponding to a plurality of BSSIDs included in a multiple BSSID set.In addition, the range of values that the BSS color may have may besmaller than the range of values that the BSSID may have. At this time,when the BSS color values of the plurality of BSSs corresponding to themultiple BSSID set are all set to be the same, it is possible to reducethe case where different BSSs do not correspond to the same multipleBSSID set but have the same BSS color value.

In another specific embodiment, when the specified BSS color is signaledin the physical layer of the received frame, the wireless communicationterminal may determine, based on the MAC address signaled in the MAClayer, whether the received frame is an Inter-BSS frame or an Intra-BSSframe.

FIG. 12 shows the channel access operation of a wireless communicationterminal according to another embodiment of the present invention.

For convenience of explanation, the BSSID of the BSS including thewireless communication terminal is referred to as a first BSSID, and thefirst BSSID and a different BSSID are referred to as a second BSSID.When the first BSSID is included in the multiple BSSID set including thesecond BSSID and the wireless communication terminal receives the PPDUtransmitted from the BSS identified by the second BSSID, the wirelesscommunication terminal may not access the corresponding channelregardless of the received signal strength. Specifically, the wirelesscommunication terminal may not access the corresponding channel whilethe PPDU transmitted from the BSS identified by the second BSSID istransmitted. At this time, the wireless communication terminal may enterthe power save state. Also, the wireless communication terminal maydetermine that the channel state is busy until it determines whether thereceived PPDU is an Inter-BSS frame or an Intra-BSS frame.

In the embodiment described in FIG. 11, the wireless communicationterminal may determine whether to access the channel according to thereceived signal strength. However, there is a high possibility that aplurality of BSSs corresponding to the multiple BSSID set are operatedby one wireless communication terminal. Therefore, while the PPDUtransmitted from the BSS identified by the second BSSID is transmitted,even when the wireless communication terminal accesses the channel andtransmits data, the access point of the BSS including the wirelesscommunication terminal may not receive the PPDU. Finally, while the PPDUtransmitted from the BSS identified by the second BSSID is transmittedregardless of the strength of the received signal, it may be effectiveto restrict the transmission of the wireless communication terminal.

In the embodiment of FIG. 12, a PPDU is transmitted from the BSSidentified by the second BSSID BSSID(2). At this time, the station STAof BSSID(1) included in the BSS identified by the first BSSID BSSID(1)that is not the second BSSID BSSID(2) determines the BSS color signaledby the PPDU. Specifically, the station STA of BSSID(1) included in theBSS identified by the first BSSID BSSID(1) may obtain the BSS color fromthe signaling field of the PPDU. Since the BSS color obtained from thesignaling field of the PPDU is the same as the BSS color of the BSSidentified by the first BSSID BSSID(1) in the station STA of BSSID(1)included in the BSS identified by the first BSSID BSSID(1), the stationSTA of BSSID(1) included in the BSS identified by the first BSSIDBSSID(1) does not access the corresponding channel regardless of thereceived signal strength value. Specifically, the station STA ofBSSID(1) included in the BSS identified by the first BSSID BSSID(1)determines that the corresponding channel is busy regardless of receivedsignal strength value. Through this operation, the wirelesscommunication terminal may prevent a transmission collision between BSSscorresponding to the same multiple BSSID set.

FIG. 13 shows a method of setting BSS color values of a plurality ofBSSs corresponding to a multiple BSSID set according to an embodiment ofthe present invention.

The BSS colors of the plurality of BSSs corresponding to the multipleBSSID set may be set to different values. The plurality of access pointsoperating each of the plurality of BSSs corresponding to the multipleBSSID set may set the BSS color values of the plurality of BSSscorresponding to the multiple BSSID set differently. In a specificembodiment, only some of a plurality of BSSs corresponding to a multipleBSSID set may be set to different BSS color values. At this time, thewireless communication terminal of the BSS corresponding to the multipleBSSID set may determine whether the recipient of the received PPDU is awireless communication terminal by decoding the signaling field of thephysical layer. Accordingly, the wireless communication terminal maydetermine that the recipient of the PPDU, which is received faster thanthe case where the BSS color values of the plurality of BSSscorresponding to the multiple BSSID set are set to be the same in thereceived PPDU, is the wireless communication terminal. When therecipient of the received PPDU is not a wireless communication terminal,the wireless communication terminal may stop decoding. At this time, thewireless communication terminal may not access the corresponding channelbased on at least one of the PPDU length, the TXOP length, and thebandwidth of the PPDU in order to protect the PPDU being transmitted.

At this time, the access point may explicitly signal BSS color values ofa plurality of BSSs corresponding to a multiple BSSID set. In anotherspecific embodiment, the BSS color values for a plurality of BSSscorresponding to the multiple BSSID set may be set according topredetermined rules. Specifically, in the BSS color values of aplurality of BSSs corresponding to multiple BSSID, one or more bitvalues corresponding to the same position may be the same. For example,in the BSS color values of a plurality of BSSs corresponding to amultiple BSSID set, n MSBs may be the same. For example, in the BSScolor values of a plurality of BSSs corresponding to a multiple BSSIDset, n LSBs may be the same. In a specific embodiment, the value of nmay be determined according to the number of BSSIDs included in themultiple BSSID set.

In FIG. 13(a), the three BSSs corresponding to the multiple BSSID sethave different BSS color values. All other settings of the network arethe same as in FIG. 9. At this time, the BSS color value may beindicated by 6 bits as shown in FIG. 13(b). Therefore, the BSS colorvalue may be in the range of 0 to 63. At this time, in the BSS colorvalues of a plurality of BSSs corresponding to the same multiple BSSIDset, n MSBs are the same.

In addition, a plurality of access points, each operating a plurality ofBSSs corresponding to a multiple BSSID set, may set BSS color values ofa plurality of BSSs corresponding to a multiple BSSID set based on aBSSID value. Specifically, a plurality of access points, each operatinga plurality of BSSs corresponding to a plurality of BSSIDs, may set aLSB as a BSS color value as many as the number of bits that the BSScolor value may have in the BSSID value. At this time, the wirelesscommunication terminal may obtain the LSBs as many as the number of bitsthat the BSS color value may have from the bit value of the BSSID as theBSS color value corresponding to the BSSID. That is, the wirelesscommunication terminal may obtain the BSS color value corresponding tothe BSSID by BSSID % 2^(n). In this case, when the wirelesscommunication terminal does not have the BSSID included in the multipleBSSID set, it may obtain the BSS color value corresponding to eachBSSID. Therefore, no separate signaling is required for the BSS colorvalues of the plurality of BSSs corresponding to the multiple BSSID set.

In another specific embodiment, a plurality of access points, operatingeach of a plurality of BSSs corresponding to a multiple BSSID set, mayset a BSS color value corresponding to a multiple BSSID set based on thereference BSSID. Specifically, the plurality of access points, operatingeach of the plurality of BSSs corresponding to a multiple BSSID, sets avalue obtained by adding a difference between a reference BSSID and acorresponding BSSID to a BSS color value corresponding to the referenceBSSID of a multiple BSSID set, as a color value corresponding to thecorresponding BSSID.

As described above, the range of a value that the BSS color may have maybe less than the range of values that the BSSID may have. At this time,when the BSS color values of the plurality of BSSs corresponding to themultiple BSSID set are all set differently, it is more possible thatBSSs that do not correspond to the same multiple BSSID set and aredifferent from each other have the same BSS color value. Therefore, whenBSS color values of a plurality of BSSs corresponding to the multipleBSSID set are all set differently, the wireless communication terminalmay perform the SR operation after checking the MAC address signaled inthe MAC layer of the received frame. At this time, the wirelesscommunication terminal may determine, based on the MAC address signaledin the MAC layer of the received frame, whether the received frame is anInter-BSS frame or an Intra-BSS frame. In addition, the SR operation mayinclude at least one of the channel access operation and the power saveoperation described above.

As described above, the wireless communication terminal may determine,based on the MAC address, whether the received frame is an Inter-BSSframe or an Intra-BSS frame. At this time, a specific method ofdetermining whether the frame received by the wireless communicationterminal is an Inter-BSS frame or an Intra-BSS frame and a power saveoperation of the wireless communication terminal will be described withreference to FIG. 14 through FIG. 15.

FIG. 14 shows a case where a wireless communication terminal accordingto an embodiment of the present invention enters a power save statebased on a MAC header of a frame received by the wireless communicationterminal. Also, FIG. 15 shows a case where, when a wirelesscommunication terminal according to an embodiment of the presentinvention is included in a BSS corresponding to a multiple BSSID set,the wireless communication terminal enters a power save state based on aMAC header of a frame received by the wireless communication terminal.

When a Transmitter Address TA or a Receiver Address RA indicated by aMAC header of a received frame corresponds to another BSSID of amultiple BSSID set that includes a BSSID of a BSS including a wirelesscommunication terminal, the wireless communication terminal maydetermine the received frame as an Intra-BSS frame. When the framereceived by the wireless communication terminal is an Intra-BSS frameand the wireless communication terminal is not a recipient of a receivedframe, the wireless communication terminal may enter the power savestate. At this time, the wireless communication terminal may maintainthe power save state until the end of the duration of the PPDU includingthe received frame.

In the embodiment of FIG. 14, the first station STA1 and the secondstation STA2 are associated with the same access point AP. When theaccess point AP transmits a PPDU to the first station STA1, the secondstation STA2 may receive the PPDU. At this time, the second station STA2determines whether the received PPDU is an intra-BSS frame. When thereceived PPDU is an Intra-BSS frame, the second station STA2 determineswhether the recipient of the received PPDU is the second station STA2.Specifically, the second station STA2 may determine, based on the MACheader, whether the recipient of the received PPDU is the second stationSTA2. At this time, when the second station STA2 is not the recipient ofthe received PPDU, the second station STA2 may enter the power savestate.

When entering the power save state, the wireless communication terminalmay determine whether the Receiver Address RA of the frame indicates aplurality of wireless communication terminals including thecorresponding wireless communication terminal. Specifically, when thereceived frame is an Intra-BSS frame, the Receiver Address RA of thereceived frame is not the MAC address of the wireless communicationterminal, and the Receiver Address RA of the received frame does notcorrespond to the broadcast address, the wireless communication terminalmay enter the power save state. At this time, when the Receiver AddressRA of the received frame does not correspond to the multicast addressthat the wireless communication terminal should receive and the ReceiverAddress (RA) of the received frame does not correspond to the groupaddress that the wireless communication terminal should receive, thewireless communication terminal may enter the power save state.

In a specific embodiment, even when the Receiver Address RA of thetrigger frame or the Receiver Address RA of a multi-station block ACK(Multi-STA BlockACK) frame does not match the MAC address of thewireless communication terminal, the wireless communication terminal mayneed to receive a trigger frame or a multi-station block ACK frame.Specifically, when the recipient of the trigger frame is a plurality ofwireless communication terminals, the Receiver Address RA of the triggerframe may be a broadcast address. At this time, the number of User Infofields of the trigger frame may be two or more. Also, when the recipientof the multi-station block ACK frame is a plurality of wirelesscommunication terminals, the Receiver Address RA of the multi-stationblock ACK may be a broadcast address. At this time, the number of AIDfields in the Per STA Info subfield of the multi-station block ACK maybe two or more. At this time, the broadcast address may indicate aplurality of wireless communication terminals or one wirelesscommunication terminal.

Accordingly, when the received frame is an Intra-BSS frame, the ReceiverAddress RA of the received frame is not the MAC address of the wirelesscommunication terminal, the received frame is a trigger frame, and theReceiver Address RA of the received frame does not correspond to thebroadcast address, the wireless communication terminal may enter thepower save state. In addition, when the received frame is an Intra-BSSframe, the Receiver Address RA of the received frame is not the MACaddress of the wireless communication terminal, the received frame is atrigger frame, and the Receiver Address RA of the multi-station blockACK frame does not correspond to the broadcast address, the wirelesscommunication terminal may enter the power save state.

Specifically, when the recipient of the trigger frame or themulti-station block ACK frame is a plurality of wireless communicationterminals, the Receiver Address RA may be a multicast address or a groupaddress. Therefore, when the wireless communication terminal receivesthe trigger frame or the multi-station block ACK frame and the ReceiverAddress RA of the received frame is not a multicast address and a groupaddress including the wireless communication terminal, the wirelesscommunication terminal may enter the power save state.

When any one of the BSSIDs included in the multiple BSSID set is set tothe Receiver Address RA of the frame or the Transmitter Address TA ofthe frame, only the wireless communication terminal included in the BSSidentified by the corresponding BSSID may be a recipient or atransmitter of the corresponding frame. Specifically, for a frametransmitted to a plurality of wireless communication terminals includedin each of two or more BSSs corresponding to a multiple BSSID set, amodified value may be set based on the BSSID in the Transmitter Addressof the frame. At this time, the wireless communication terminal may notseparately determine whether the Receiver Address RA and the TransmitterAddress TA are the broadcast address or the multicast address includingthe address of the wireless communication terminal. For convenience ofexplanation, the BSSID of the BSS including the wireless communicationterminal is referred to as a first BSSID, and a different BSSID otherthan the first BSSID is referred to as a second BSSID. Specifically,when the second BSSID is included in the multiple BSSID set includingthe first BSSID and the Receiver Address RA or the Transmitter AddressTA of the frame received by the wireless communication terminal matchesthe second BSSID, the wireless communication terminal may enter thepower save state.

In the embodiment of FIG. 15, the multiple BSSID set includes a firstBSSID BSSID(1) and a second BSSID BSSID(2). The first station STA1 isincluded in the BSS identified by the second BSSID BSSID(2) and thesecond station STA2 is included in the BSS identified by the first BSSIDBSSID(1). At this time, the virtual access point having the second BSSIDBSSID(2) transmits the PPDU to the first station STA1. The secondstation STA2 receives the corresponding PPDU. The second station STA2determines whether the received PPDU is an intra-BSS frame.Specifically, the second station STA2 may determine whether the MACaddress signaled by the MAC header of the received PPDU is the BSSID ofthe multiple BSSID set including the first BSSID. Since the TransmitterAddress TA of the received PPDU is the second BSSID BSSID(2), the secondstation STA2 determines the received PPDU as an intra-BSS frame. Also,since the recipient of the received PPDU is a wireless communicationterminal included in the BSS identified by the second BSSID BSSID(2),the second station STA2 enters the power save state.

When the received PPDU is an Inter-BSS frame, the second station STA2determines whether the recipient of the received PPDU is the secondstation STA2. Specifically, the second station STA2 may determinewhether the recipient of the PPDU received based on the MAC header isthe second station STA2. At this time, when the second station STA2 isnot the recipient of the received PPDU, the second station STA2 mayenter the power save state.

In another specific embodiment, when the reference BSSID is set to theTransmitter Address (TA) of the frame, it may indicate that theTransmitter Address TA is transmitted to a plurality of wirelesscommunication terminals included in two or more BSSs corresponding tothe multiple BSSID set. When the second BSSID is included in themultiple BSSID set including the first BSSID, the second BSSID is notthe reference BSSID, and the Receiver Address RA or the TransmitterAddress TA of the frame received by the wireless communication terminalindicates that the frame is transmitted from the second BSSID, thewireless communication terminal may enter the power save state.

When a multiple BSSID set is used, a wireless communication terminal mayincrease the efficiency of transmission of other types of frame as wellas a management frame. This will be described with reference to FIGS. 16to 18.

FIG. 16 shows a method of displaying an identifier of a wirelesscommunication terminal included in a plurality of BSSs corresponding toa multiple BSSID set according to an embodiment of the presentinvention.

The wireless communication terminal may signal the wirelesscommunication terminal to receive data by using the signaling field ofthe physical layer. Specifically, the wireless communication terminalmay signal a wireless communication terminal to receive data throughtransmission using the MU-MIMO by using the signaling field of thephysical layer. Also, the wireless communication terminal may signal awireless communication terminal to receive data by using a TrafficIndicator Map (TIM). In this case, a method of signaling one or aplurality of wireless communication terminals included in the BSScorresponding to multiple BSSIDs may be a problem.

The wireless communication terminal may signal a plurality of wirelesscommunication terminals included in the BSS corresponding to multipleBSSIDs using a bitmap. Each bit of the bitmap indicates a wirelesscommunication terminal, and when the value of the bit is 1, the bitmapsignals a wireless communication terminal corresponding to thecorresponding bit. At this time, the bitmap may be mapped to anAssociation identifier (AID) of the wireless communication terminal.Also, a plurality of wireless communication terminals operating aplurality of BSSs corresponding to the multiple BSSID set may allocatebits of the bitmap from 0 to X to a plurality of wireless communicationterminals included in a plurality of BSSs corresponding to the multipleBSSID set. In this case, X may be a value obtained by subtracting 1 fromthe maximum value of the BSSID that may be included in the multipleBSSID set. Specifically, X may be 2^(n)−1, and n may be the value of theMaxBSSID indicator field described above. At this time, when signaling aplurality of wireless communication terminals included in any one of theplurality of BSSs corresponding to the multiple BSSID set, the wirelesscommunication terminal may set the bit of the association identifier ofthe wireless communication terminal operating the corresponding BSSto 1. At this time, the specific form of the bitmap may be the same asthat of the embodiment of FIG. 16(a). In addition, a specific bit of thebitmap may indicate all wireless communication terminals included in aplurality of BSSs corresponding to a multiple BSSID set. At this time,the specific bit may be a bit corresponding to the associationidentifier 2007.

When using the method described above, the wireless communicationterminal should signal all the wireless communication terminals includedin one of the plurality of BSSs corresponding to the multiple BSSID setor signal all wireless communication terminals included in the pluralityof BSSs corresponding to the multiple BSSID set. Therefore, thecombination of wireless communication terminals that a wirelesscommunication terminal may signal may be limited. Accordingly, thewireless communication terminal may allocate some bits of the bit mapdescribed above as group bits indicating the group of wirelesscommunication terminals. At this time, the group may be a groupincluding some BSSs among a plurality of BSSs corresponding to amultiple BSSID set. Also, the group may be a group including some of aplurality of wireless communication terminals included in a plurality ofBSSs corresponding to the multiple BSSID set. At this time, the specificform of the bitmap may be the same as that of the embodiment of FIG.16(a).

Also, the wireless communication terminal may use the AID allocationmethod of the multiple BSSID TIM operation to reduce the bitmap size.Specifically, the Bitmap Control field of FIGS. 16(a) and 16(b) may beutilized. Further, when the maximum number of groups that the wirelesscommunication terminal may use is limited, it is possible to transmit abitmap allocatable to a group and not to transmit a bitmap correspondingto the remaining association identifier. The wireless communicationterminal may transmit the bitmap through an association response frameand a reassociation response frame. Further, the wireless communicationterminal may signal the information on the group through the managementframe or the action frame. Specifically, the wireless communicationterminal may signal an association identifier corresponding to a groupthrough an association response frame and a reassociation responseframe.

FIG. 17 shows a trigger frame format according to an embodiment of thepresent invention.

The wireless communication terminal may trigger the transmission of aplurality of wireless communication terminals by transmitting a triggerframe. The specific format of the trigger frame may be the same as thatof the embodiment of FIG. 17. The trigger frame may include aTransmitter Address field A2 indicating a Transmitter Address, which isthe address of a wireless communication terminal that transmits thetrigger frame. Since the case where a wireless communication terminaloperating a BSS transmits a trigger frame is general, it is general thatthe Transmitter Address of the trigger frame is set to the BSSID of BSSfrom which the trigger frame is transmitted.

The wireless communication terminal may trigger the transmission of aplurality of wireless communication terminals included in a plurality ofBSSs corresponding to the multiple BSSID set through one trigger frame.Specifically, the wireless communication terminal may trigger thetransmission of a plurality of wireless communication terminals includedin a plurality of BSSs corresponding to the multiple BSSID set bysetting the Transmitter Address of the trigger frame to the referenceBSSID. However, in this embodiment, a case of triggering a plurality ofwireless communication terminals included in a BSS corresponding to areference BSSID and a case of triggering a plurality of wirelesscommunication terminals included in a plurality of BSSs corresponding toa multiple BSSID set may not be distinguished from each other. Toprevent this, the wireless communication terminal may set theIndividual/Group of the reference BSSID to 1. Therefore, the wirelesscommunication terminal may set the reference BSSID in whichIndividual/Group is 1 as the Transmitter Address to trigger thetransmission of the plurality of wireless communication terminalsincluded in the plurality of BSSs corresponding to the multiple BSSIDset.

In another specific embodiment, the wireless communication terminal setsa value of n LSBs set to 0 in the reference BSSID as a TransmitterAddress to trigger the transmission of a plurality of wirelesscommunication terminals included in a plurality of BSSs corresponding tothe multiple BSSID set. In this case, n may be the value of the MaxBSSIDindicator field described above. However, when there is a BSS having avalue of n LSBs set to 0 in the reference BSSID as a BSSID, confusionmay occur with respect to the BSS indicated by the Transmitter Address.

FIG. 18 shows a trigger frame format according to another embodiment ofthe present invention.

In the embodiment of FIG. 17, when the Transmitter Address of thetrigger frame indicates a plurality of BSSs corresponding to a multipleBSSID set, it is necessary to check that all the wireless communicationterminals included in the plurality of BSSs corresponding to themultiple BSSID set trigger the transmission of the correspondingwireless communication terminal by the trigger frame. The wirelesscommunication terminal signals a BSS including a terminal triggeredthrough a Transmitter Address of a trigger frame to trigger thetransmission of a wireless communication terminal included in some of aplurality of BSSs corresponding to a multiple BSSID set. Specifically,the wireless communication terminal may set the Transmitter Address ofthe trigger frame to any one of a plurality of BSSIDs included in themultiple BSSID set. Through this, the wireless communication terminalmay trigger the transmission of a plurality of wireless communicationterminals included in the BSS identified by the BSSID having a valuelarger than the corresponding BSSID among the plurality of BSSIDsincluded in the multiple BSSID set. In another embodiment, the wirelesscommunication terminal may trigger the transmission of a plurality ofwireless communication terminals included in the BSS identified by theBSSID having a value smaller than the corresponding BSSID among theplurality of BSSIDs included in the multiple BSSID set.

At this time, the wireless communication terminal may transmit signalinginformation indicating the triggering of the transmission of wirelesscommunication terminals included in some BSSs among a plurality of BSSscorresponding to a multiple BSSID set. Specifically, by using asignaling field set to 0 when a wireless communication terminaltransmits a control frame, the wireless communication terminal maytransmit the signaling information. Specifically, the wirelesscommunication terminal may transmit the signaling information by settingthe Order subfield of the Frame Control field of the MAC frame formatto 1. In another specific embodiment, the wireless communicationterminal may transmit the signaling information by setting theIndividual/Group bit of a Receiver Address or a Transmitter Addressto 1. In another specific embodiment, the wireless communicationterminal may set the control frame to 0 and set the To DS or From DSsubfield of the Frame Control field of the MAC frame format to 1 totransmit the signaling information.

The wireless communication terminal sets the Transmitter Address of thetrigger frame to one of a plurality of BSSIDs included in the multipleBSSID set and signals the offset value. Through this, the wirelesscommunication terminal may trigger the transmission of a wirelesscommunication terminal included in the BSS corresponding to the BSSID ofan offset value from the corresponding BSSID among the plurality ofBSSIDs included in the multiple BSSID set. At this time, the wirelesscommunication terminal may signal an offset by combining several 1-bitfields used in the above-described transmission method of signalinginformation.

In another specific embodiment, the wireless communication terminal maysignal a BSS including a wireless communication terminal triggered by atrigger frame by setting the Receiver Address of the trigger frame witha bitmap to which a plurality of BSSIDs included in the multiple BSSIDset are mapped. At this time, the wireless communication terminal mayset the bit corresponding to the BSS including the triggered wirelesscommunication terminal in the bitmap to 1. The specific trigger frameformat may be the same as in FIG. 18.

FIG. 19 shows a trigger frame format according to another embodiment ofthe present invention.

The wireless communication terminal receiving the trigger frame maytransmit the trigger-based PPDU. At this time, a non-associated wirelesscommunication terminal may receive the trigger frame and transmit thetrigger-based PPDU. When the wireless communication terminal receivingthe trigger frame transmits the trigger-based PPDU, the wirelesscommunication terminal receiving the trigger frame may signal the BSScolor through the signaling field of the physical layer of the PPDU. Anon-associated wireless communication terminal may set the BSS colorvalue indicated by the signaling field based on the BSS color signaledin the physical layer of the trigger frame. However, when the PPDUincluding the trigger frame is a legacy PPDU, the BSS color in thesignaling field of the PPDU including the trigger frame may not besignaled. Therefore, the wireless communication terminal may signal theBSS color in the MAC layer of the trigger frame. Accordingly, thewireless communication terminal receiving the trigger frame may signalthe BSS color value signaled in the MAC layer of the trigger framethrough the signaling field of the trigger-based PPDU. Specifically, thewireless communication terminal may signal the BSS color in the CommonInfo field of the MAC layer of the trigger frame. At this time, theCommon Info field is a field for signaling information commonly appliedto a plurality of wireless communication terminals triggered by thetrigger frame. In a specific embodiment, when the wireless communicationterminal transmits a trigger frame allowing random access, the wirelesscommunication terminal may signal the BSS color in the MAC layer of thetrigger frame. For example, when a wireless communication terminaltransmits a trigger frame allowing random access to a non-associatedwireless communication terminal, the wireless communication terminal maysignal the BSS color in the MAC layer of the trigger frame. In addition,when the BSS color is signaled in the MAC layer of the trigger frame,the wireless communication terminal receiving the trigger frame maydetermine the trigger frame as a trigger frame for random access.Specifically, when the BSS color is signaled in the MAC layer of thetrigger frame, the wireless communication terminal receiving the triggerframe may determine the corresponding trigger frame as a trigger framefor random access of a non-associated wireless communication terminal.

Also, the wireless communication terminal may signal whether the BSScolor is signaled in the MAC layer of the trigger frame through thephysical layer of the trigger frame. Specifically, the wirelesscommunication terminal may vary the value of the duration field of theMAC layer of the trigger frame to signal whether the BSS color issignaled in the MAC layer of the trigger frame. In a specificembodiment, when the BSS color is signaled in the MAC layer of thetrigger frame, the wireless communication terminal may set the value ofthe Duration field of the MAC layer to be larger than the value of theDuration field of the MAC layer set when the BSS color is not signaledin the MAC layer of the trigger frame. In another specific embodiment,the wireless communication terminal may vary the indication bit of theFrame Control (FC) of the MAC layer of the trigger frame to signalwhether the BSS color is signaled in the MAC layer of the trigger frame.

FIG. 20 shows an OFDMA backoff operation of a wireless communicationterminal according to an embodiment of the present invention.

The plurality of wireless communication terminals may transmit data toany one of the wireless communication terminals using OrthogonalFrequency Division Multiplexing Access (OFDMA). At this time, theplurality of wireless communication terminals may transmit data to anyone of the wireless communication terminals based on the trigger frame.In a specific embodiment, the trigger frame may signal a frequency bandthat a plurality of wireless communication terminals may randomlyaccess. At this time, a plurality of wireless communication terminalsmay use a random value to distribute the accesses of the plurality ofwireless communication terminals. Specifically, each of the plurality ofwireless communication terminals may obtain a random value in an OFDMAContention Window (OCW) and set the random value as an OFDMA backoff(OBO) counter. At this time, the OCW is a natural number. In a specificembodiment, the OCW may be adjusted according to the channel accessmethod and traffic characteristics. The plurality of wirelesscommunication terminal may reduce OBO counter value by the number ofresource units (RUs) to which the random access is allowed signaled bythe trigger frame. At this time, the RU may indicate a unit of afrequency band that the wireless communication terminal may access fordata transmission. When the OBO counter value reaches 0, the wirelesscommunication terminal may access the RU to which the random accesssignaled by the trigger frame is allowed. When there are a plurality ofRUs to which random access is allowed, the wireless communicationterminal may randomly select any one of a plurality of RUs to whichrandom access is allowed. In addition, when the wireless communicationterminal transmits the trigger frame, the wireless communicationterminal may allocate a predetermined association identifier (AID) valueto the RU to which random access is allowed.

The wireless communication terminal may reduce the OBO counter valuebased on the BSS including the wireless communication terminal and theBSS to which the trigger frame is transmitted. Specifically, when atrigger frame is transmitted from the same BSS as the BSS including thewireless communication terminal, the wireless communication terminal mayreduce the OBO counter value based on the trigger frame. In anotherspecific embodiment, when the trigger frame triggers the transmission ofa plurality of wireless communication terminals included in one of theplurality of BSSs corresponding to the multiple BSSID sets or one ormore BSSs, the wireless communication terminal included in the same BSSas at least one of the plurality of triggered wireless communicationterminals may reduce the OBO counter value based on the trigger frame.In another specific embodiment, a non-associated wireless communicationterminal may reduce the OBO counter value based on the trigger frameregardless of the BSS from which the trigger frame is transmitted. Atthis time, when there is a recipient that a non-associated wirelesscommunication terminal is to transmit a frame, the non-associatedwireless communication terminal may reduce the OBO counter value basedonly on the trigger frame transmitted from the BSS including thecorresponding recipient. For example, when a non-associated wirelesscommunication terminal is to transmit an association request frame, thenon-associated wireless communication terminal may reduce the OBOcounter value based on only the trigger frame transmitted from the BSSto which the recipient of the associate request frame belongs. At thispoint, when a non-associated wireless communication terminal is totransmit a probe request frame, the non-associated wirelesscommunication terminal may reduce the OBO counter value based on onlythe trigger frame regardless of the BSS from which the trigger frame istransmitted.

FIG. 20(a) shows an associate relationship between a first access pointAP 1, a second access point AP 2, a first station STA 1, and an x-thstation STA x. The first access point AP 1 and the first station STA 1are associated, and the x-th station STA x is not associated with anyaccess point. FIG. 20(b) shows an operation in which the first stationSTA 1 and the x-th station STA x perform random access using OFDMA. Atthis time, the first station STA 1 obtains 10 as the OBO counter value.The x-th station STA x obtains 14 as the OBO counter value. The firstaccess point AP 1 transmits a trigger frame TF-R signaling that threeRUs are allowed to be randomly accessed. At this time, since the firststation STA 1 is associated with the first access point AP 1, the OBOcounter is reduced by 3 and the OBO counter is set to 7 based on thetrigger frame TF-R. Also, since the x-th station STA x is not associatedwith any access point, the OBO counter is reduced by 3 and the OBOcounter is set to 11. The first access point AP 2 transmits a triggerframe TF-R signaling that five RUs are allowed to be randomly accessed.At this time, since the trigger frame is transmitted in the BSS otherthan the BSS including the first station STA 1, the first station STA 1does not reduce the OBO counter value. Since the x-th station STA x isnot associated with any access point, the OBO counter is reduced by 5and the OBO counter is set to 6. At this time, the station x STA x mayreduce the OBO counter value according to a frame to be transmitted bythe station x STA x. Specifically, when the station x STA x transmits aprobe request frame, the station x STA x may reduce the OBO counterregardless of the access point that transmits the trigger frame. Also,when the station x STA x transmits an associate request frame, thestation x STA x may reduce the OBO counter only when the access pointthat transmits the trigger frame is the access point to receive theassociate request frame.

FIG. 21 shows the operation of a wireless communication terminalaccording to an embodiment of the present invention.

The wireless communication terminal receives the frame (S2101).Specifically, the wireless communication terminal may receive the PPDUand obtain the frame from the PPDU.

The wireless communication terminal accesses the channel according towhether the received frame is an Intra-BSS frame or an Inter-BSS frame(S2103). When a multiple BSSID set is used, the wireless communicationterminal may regard a plurality of BSSs identified by each of theplurality of BSSIDs included in the same multiple BSSID set as the sameBSS. When a multiple BSSID set is used, the wireless communicationterminal may regard a plurality of BSSs identified by each of theplurality of BSSIDs included in the same multiple BSSID set as the sameBSS. For example, the BSS of the wireless communication terminal may bea first BSS and the first BSS may correspond to a multiple BSSidentifier (BSSID) set. At this time, the wireless communicationterminal may regard the frame transmitted from the second BSScorresponding to the corresponding multiple BSSID as an intra-BSS frame.A multiple BSSID set is a set of BSSIDs of a plurality of BSSsclassified into one group. Specifically, a plurality of BSSscorresponding to a multiple BSSID set may use the same channel. Inaddition, a plurality of BSSs corresponding to a multiple BSSID set maybe operated by one wireless communication terminal.

The wireless communication terminal may determine, based on the BSScolor, whether the received frame is an Intra-BSS frame or an Inter-BSSframe. Therefore, a plurality of BSSs corresponding to the same multipleBSSID set may all have the same BSS color value. At this time, the BSScolor may be information for identifying the BSS signaled through thephysical layer of the frame. Specifically, the BSS color values of aplurality of BSSs corresponding to a multiple BSSID set may be set inthe same manner as in the embodiment described with reference to FIG. 9through FIG. 12. Through this, the wireless communication terminal mayprocess a plurality of BSSs identified by the plurality of BSSIDsincluded in the multiple BSSIDs as the same BSS.

In another specific embodiment, each of the plurality of BSSscorresponding to the multiple BSSID set may have different BSS colorvalues. At this time, the wireless communication terminal may obtain theBSS color values of the plurality of BSSs corresponding to the multipleBSSID sets through various signaling methods. At this time, thesignaling method may be the same as that of the embodiment describedwith reference to FIG. 8 and FIG. 13.

The wireless communication terminal may determine, based on the MACaddress signaled in the MAC layer, whether the received frame is anIntra-BSS frame or an Inter-BSS frame. At this time, the wirelesscommunication terminal may determine, based on the address field of thereceived frame, whether the received frame is an Inter-BSS frame or anIntra-BSS frame. Specifically, the wireless communication terminal maydetermine whether the received frame is an Intra-BSS frame or anInter-BSS frame based on the MAC address signaled in the MAC layer ofthe received frame and the plurality of BSSIDs included in the multipleBSSID set. In a specific embodiment, when a MAC address signaled in aMAC layer of a frame received by a wireless communication terminalmatches one of a plurality of BSSIDs included in a multiple BSSID set,the wireless communication terminal may determine the received frame asan Intra-BSS frame. For example, when the Transmitter Address orReceiver Address signaled in the MAC layer of the frame received by thewireless communication terminal corresponds to another BSSID of themultiple BSSID set, the wireless communication terminal may determinethe received frame as an Intra-BSS frame. At this time, the MAC addresssignaled in the MAC layer may be signaled with an Individual/Group bitindicating whether the MAC address is a group MAC address. In this case,the wireless communication terminal may determine whether the MACaddress signaled in the MAC layer except for the Individual/Group bitmatches the MAC address of the access point operating the BSS includingthe wireless communication terminal or the BSSID of the BSS includingthe wireless communication terminal. In addition, when the MAC addresssignaled in the MAC layer of the frame received by the wirelesscommunication terminal is not matched with any one of the plurality ofBSSIDs included in the multiple BSSID set including the BSSID of the BSSincluding the wireless communication terminal, the wirelesscommunication terminal may determine the received frame as an Inter-BSSframe.

When the received frame is an Intra-BSS frame and the recipient of thereceived frame is not a wireless communication terminal, the wirelesscommunication terminal may enter the power save state. At this time,when the MAC address signaled at the MAC layer of the frame received bythe wireless communication terminal is matched with any one of theplurality of BSSIDs included in the multiple BSSID set and the recipientof the received frame is not a wireless communication terminal, thewireless communication terminal may enter the power save state.Specifically, when the Receiver Address or the Transmitter Address ofthe frame received by the wireless communication terminal is any one ofa plurality of BSSIDs included in the multiple BSSID set and theReceiver Address of the received frame is not the MAC address of thewireless communication terminal, the wireless communication terminal mayenter the power save state. At this time, the wireless communicationterminal may maintain the power save state until the end of the durationof the PPDU including the received frame. When the wirelesscommunication terminal determines whether or not entering the power savestate, the wireless communication terminal may determine whether theReceiver Address is an address indicating a plurality of wirelesscommunication terminals including a wireless communication terminal. Theaddress indicating a plurality of wireless communication terminalsincluding the wireless communication terminal may be at least one of thebroadcast address, the multicast address, and the group addressdescribed above. Specifically, the wireless communication terminal mayoperate in the same manner as the embodiments described with referenceto FIG. 10 and FIGS. 14 and 15.

Also, the wireless communication terminal may apply a different CCAthreshold value according to whether the received frame is an Inter-BSSframe or an Intra-BSS frame. For convenience of explanation, a BSScorresponding to the multiple BSSID set that the first BSS correspondsis referred to as a second BSS, and a BSS not corresponding to themultiple BSSID set that the first BSS corresponds is referred to as athird BSS. When the frame received by the wireless communicationterminal is transmitted from the second BSS, the wireless communicationterminal may apply the general CCA level not the OBSS CCA level as theCCA threshold value. When the frame received by the wirelesscommunication terminal is transmitted from the third BSS, the wirelesscommunication terminal may apply the OBSS CCA level as the CCA thresholdvalue. In another specific embodiment, when the frame received by thewireless communication terminal is transmitted from the second BSS, thewireless communication terminal may not access the corresponding channelregardless of the received signal strength. Specifically, the wirelesscommunication terminal may operate as in the embodiment described withreference to FIGS. 8, 11, and 12.

In addition, the wireless communication terminal may change the NAVsetting depending on whether the received frame is an Intra-BSS frame oran Inter-BSS frame. Specifically, the wireless communication terminalmay separately set the NAV for the intra-BSS frame and the NAV for theinter-BSS frame. At this time, when the wireless communication terminalreceives the Intra-BSS frame, the wireless communication terminal mayset or update the NAV for the intra-BSS frame based on the receivedIntra-BSS frame. In addition, when the wireless communication terminalreceives the Inter-BSS frame, the wireless communication terminal mayset or update the NAV for the inter-BSS frame based on the receivedInter-BSS frame. For convenience of explanation, a BSS corresponding tothe multiple BSSID set that the first BSS corresponds is referred to asa second BSS, and a BSS not corresponding to the multiple BSSID set thatthe first BSS corresponds is referred to as a third BSS. When thewireless communication terminal receives the frame transmitted from thesecond BSS, the wireless communication terminal may set or update theNAV for the Intra-BSS frame based on the frame transmitted from thesecond BSS. When the wireless communication terminal receives the frametransmitted from the second BSS, the wireless communication terminal mayset or update the NAV for the Intra-BSS frame based on the frametransmitted from the second BSS. In a specific embodiment, when thewireless communication terminal receives the CF-END frame from the OBSS,the wireless communication terminal may not reset the NAV for theIntra-BSS frame. Accordingly, when the wireless communication terminalreceives the CF-END frame transmitted from the second BSS identified bythe second BSSID, the wireless communication terminal may reset the NAVfor the Intra-BSS frame and maintain the NAV for the inter-BSS frame asbefore. When the wireless communication terminal receives the CF-ENDframe transmitted from the third BSS, the wireless communicationterminal may reset the NAV for the inter-BSS frame and maintain the NAVfor the intra-BSS frame as before.

Although the present invention is described by using wireless LANcommunication as an example, it is not limited thereto and may beapplied to other communication systems such as cellular communication.Additionally, while the method, device, and system of the presentinvention are described in relation to specific embodiments thereof,some or all of the components or operations of the present invention maybe implemented using a computer system having a general purpose hardwarearchitecture.

The features, structures, and effects described in the above embodimentsare included in at least one embodiment of the present invention and arenot necessary limited to one embodiment. Furthermore, features,structures, and effects shown in each embodiment may be combined ormodified in other embodiments by those skilled in the art. Therefore, itshould be interpreted that contents relating to such combination andmodification are included in the range of the present invention.

While the present invention is described mainly based on the aboveembodiments but is not limited thereto, it will be understood by thoseskilled in the art that various changes and modifications are madewithout departing from the spirit and scope of the present invention.For example, each component specifically shown in the embodiments may bemodified and implemented. It should be interpreted that differencesrelating to such modifications and application are included in the scopeof the present invention defined in the appended claims.

1-20. (canceled)
 21. A wireless communication terminal that communicateswirelessly, the terminal comprising: a transceiver; and a processor,wherein a basic service set (BSS) of the wireless communication terminalcorresponds to a multiple BSS identifier (BSSID) set, wherein themultiple BSSID set is a set of a BSSID of each of a plurality of BSSsclassified into one group, wherein the processor is configured to:receive a first frame through the transceiver, determine the first frameas an Intra-BSS frame when a medium access control (MAC) addresssignaled in a MAC header of the first frame matches any one of aplurality of BSSIDs included in the multiple BSSID set, sense a signalstrength while receiving the first frame, determine, according tocomparing the signal strength with a threshold, whether to transmit asecond frame while the first frame is being transmitted, wherein a valueof the threshold is determined based on the determining the first frameas the Intra-BSS frame, and transmit the second frame based on thedetermining whether to transmit the second frame.
 22. The wirelesscommunication terminal of claim 21, wherein the processor is configuredto apply a first threshold to the determining whether to transmit thesecond frame when the first frame is the Intra-BSS frame, and apply asecond threshold to the determining whether to transmit the second framewhen the first frame is the Inter-BSS frame, wherein the secondthreshold is determined in a Overlapped BSS (OBSS) level range, whereinthe OBSS level range includes values equal to or greater than the firstthreshold.
 23. The wireless communication terminal of claim 21, whereinwhen a transmitter address (TA) or a receiver address (RA) signaled inthe MAC header of the first frame matches any one of the plurality ofBSSIDs included in the multiple BSSID set, the processor is configuredto determine that the first frame is an Intra-BSS frame.
 24. Thewireless communication terminal of claim 21, wherein the processor isconfigured to enter a power save state when the first frame is anIntra-BSS frame and a receiver address (RA) of the first frame does notindicate the wireless communication terminal.
 25. The wirelesscommunication terminal of claim 21, wherein the processor is configuredto maintain the power save state during a duration of a PLCP ProtocolData Unit (PPDU) including the first frame.
 26. The wirelesscommunication terminal of claim 21, wherein the processor is configuredto separately set a Network Allocation Vector (NAV) for an Intra-BSSframe and a NAV for an Inter-BSS frame and access a channel based on theNAV for the Intra-BSS frame and the NAV for the Inter-BSS frame.
 27. Thewireless communication terminal of claim 26, wherein when the MACaddress signaled in the MAC header of the first frame matches any one ofthe plurality of BSSIDs included in the multiple BSSID set, theprocessor is configured to set the NAV for the Intra-BSS frame based onthe first frame.
 28. The wireless communication terminal of claim 21,wherein values of BSS colors corresponding to the plurality of BSSs arethe same as each other, and the BSS color is information identifying aBSS signaled in a physical layer signaling field of a PLCP Protocol DataUnit (PPDU) including the first frame.
 29. An operating method of awireless communication terminal that communicates wirelessly, the methodcomprising: receiving a first frame; determining the first frame as anIntra-BSS frame when a medium access control (MAC) address signaled in aMAC header of the first frame matches any one of a plurality of BSSIDsincluded in a multiple basic service set identifier (BSSID) set to whicha BSS of the wireless communication terminal corresponds, wherein themultiple BSSID set is a set of a BSSID of each of a plurality of BSSsclassified into one group; sensing a signal strength while receiving thefirst frame; determining, according to comparing the signal strengthwith a threshold, whether to transmit a second frame while the firstframe is being transmitted, wherein a value of the threshold isdetermined based on determining the first frame as the Intra-BSS frame;and performing the transmission based on the determining whether totransmit the second frame.
 30. The method of claim 29, the methodfurther comprises applying a first threshold to the determining whetherto transmit the second frame when the first frame is the Intra-BSSframe, and applying a second threshold to the determining whether totransmit the second frame when the first frame is the Inter-BSS frame,wherein the second threshold is determined within a OBSS level range,wherein the OBSS level range is equal to or greater than the firstthreshold.
 31. The method of claim 29, wherein the determining the firstframe as the Intra-BSS frame comprises determining that the first frameis an Intra-BSS frame when a transmitter address (TA) or a receiveraddress (RA) signaled in the MAC header of the first frame matches anyone of the plurality of BSSIDs included in the multiple BSSID set. 32.The method of claim 29, the method further comprises entering a powersave state when the first frame is an Intra-BSS frame and a receiveraddress (RA) of the first frame does not indicate the wirelesscommunication terminal.
 33. The method of claim 29, wherein the enteringthe power save state comprises maintaining the power save state during aduration of a PLCP Protocol Data Unit (PPDU) including the first frame.34. The method of claim 29, the method further comprises separatelysetting a Network Allocation Vector (NAV) for an Intra-BSS frame and aNAV for an Inter-BSS frame and access a channel based on the NAV for theIntra-BSS frame and the NAV for the Inter-BSS frame.
 35. The method ofclaim 34, wherein the separately setting the NAV comprises setting theNAV for the Intra-BSS frame based on the first frame when the MACaddress signaled in the MAC header of the first frame matches any one ofthe plurality of BSSIDs included in the multiple BSSID set.
 36. Themethod of claim 29, wherein values of BSS colors corresponding to theplurality of BSSs are the same as each other, and the BSS color isinformation identifying a BSS signaled in a physical layer signalingfield of a PLCP Protocol Data Unit (PPDU) including the first frame.